The invention relates to improvements in methods of and in apparatus for making rod-shaped articles of the tobacco processing industry. More particularly, the invention relates to improvements in methods of and in apparatus for making elongated rod-shaped bodies from continuous flows (such as streams or tows, hereinafter called tows) of fibrous material. Typical examples of rod-shaped bodies which can be produced in accordance with the method and apparatus of the present invention are filter rods which are to be subdivided into filter rod sections of unit length or multiple unit length for attachment to plain cigarettes, cigars or cigarillos.
It is well known to monitor the characteristics of elongated rod-shaped bodies which are to be subdivided into rod-shaped articles of the tobacco processing industry. For example, a continuous tobacco filler which is to be converted into a cigarette rod is normally monitored for density, and appropriate corrective undertakings are carried out if the density deviates from an acceptable range of densities. It is also known to ascertain the resistance which a tobacco filler or a filler of fibrous filter material offers to axial and/or transverse flow of air because this furnishes information concerning the resistance which is encountered by tobacco smoke during flow from the lighted end of a cigarette, cigar, cigarillo or cheroot toward and into the mouth of the smoker. Still further, it is known to pneumatically test coherent or discrete rod-shaped articles of the tobacco processing industry in order to ascertain the hardness of their fillers.
Irrespective of the exact nature of the testing operation, the results of the test or tests are used to indicate the monitored characteristic or characteristics and/or to adjust the apparatus in order to ensure that the characteristic or characteristics are altered when they depart from acceptable values. For example, pneumatic measurements of resistance which a rod of fibrous smoking or filter material offers to the flow of air therethrough can be used for the generation of signals which influence the operation of the rod making machine in a sense to ensure that the resistance of the ultimate product (such as filter rod sections or plain cigarettes) will match or closely approximate the optimum resistance.
Commonly owned U.S. Pat. No. 3,971,695 to Block discloses a method of and an apparatus for making filter plugs. The apparatus is equipped with a testing device which ascertains the resistance of filter plugs to axial flow of air therethrough. The patented apparatus is further equipped with means for ascertaining the resistance to the flow of air through the unwrapped filler of a filter rod and to regulate the quantity of filter tow in the rod in dependency on the results of the testing operation. The results of such testing operation can also be used to regulate the extent to which the filaments of the tow are stretched ahead of the compacting station and/or to regulate the rate of speed at which the filler is draped into a web of wrapping material.
A filter rod making machine employs an endless conveyor belt, also called garniture belt, which transports successive increments of the tow of fibrous filter material and a web of wrapping material through a combined compacting or condensing and wrapping station where the compacted tow and the web are converted into a continuous filter rod. The rod is thereupon subdivided into filter rod sections of unit length or multiple unit length, and such sections are introduced into a tipping machine which turns our filter cigarettes, cigarillos or cigars. It has been found that the conveyor belt is subject to extensive wear and that such wear influences the accuracy of pneumatic testing operation or operations which are carried out upon the tow or filler in the region where the tow or filler is transported by the belt. Thus, testing fluid is likely to escape from the wrapping mechanism at a rate which is directly related to the extent of wear upon the belt. This can distort the results of measurements and can entail inaccurate adjustments of the maker so that the characteristics (such as the resistance to flow of tobacco smoke) of ultimate products depart from acceptable characteristics. Uncontrolled escape of testing fluid can also influence the results of measurements which are carried out in order to ascertain the hardness of the filler in the region where the filler is transported by the belt.